Optical character recognition (OCR) of black-and-white images is known. However, the popularity of color documents has created a need for text recognition of gray level and/or color characters, often with a complex background. For example, text with background of this type may often be found in advertisements and magazine articles. Sometimes, text is encountered that is on a complex textured background, or the background gradually changes from one color to another. This type of background is difficult to handle with traditional global thresholding methods.
More particularly, global thresholding methods are utilized in at least one current optical character recognition (OCR) software package. The generation of a single global threshold for an entire image is fast and simple. However, a global threshold provides satisfactory results only when an image has a highly even background. Even with user intervention, OCR software with global thresholding cannot handle images with uneven illumination or complicated backgrounds such as a textured background.